Synonyms:
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Splenic fever, Milzbrand, charbon, wool sorters disease, malignant carbuncle
• a peracute, acute, infectious & septicaemic disease
• Disease of cattle & sheep
• Sudden death
• Zooanthroponosis - Disease spread from infected animals human
• Extensive enlargement ®spleen - the name splenic fever - cattle
• Bacillus anthracis - an agent of bio-terrorism
• Anthrax - a reportable disease requiring the involvement of government regulatory agencies to diagnose & confirm the disease:
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ETIOLOGY
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Bacillus anthracis- a pathogenic strains
• Listed a category A disease ® US Centre for Disease Control and Prevention
• gram positive, a non motile, capsulated, aerobic, spore forming straight, very large rod shaped organism & in a small short chain
• Spores produce on exposure ® oxygen/air - live for a long time in the environment.
• The organism has two virulent factors :
• a poly D-glutamic acid capsule (encoded by virulent plasmid pxo2)
• A triple toxin - which encompasses edema, lethal & protective antigen ( plasmid pXo1)
Source of infection:
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• Accidental ingestion - bone meal, tannery effluents, fodders from infected soil digging of old anthrax grave
• Calcium rich & alluvial soil , alkaline soil (pH 9.0)- great risk
• Acid soil destroy the organism.
TRANSMISSION-
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• Ingestion, halation skin penetration
• Inhalation is important mode of spread in human - wool sorters disease
• Persons - working in wool & hair industries are mostly affected.
• Mechanical transmission ® Tabanid fly bite
Host affected:
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• cattle & sheep - highly susceptible than goat & horses
• Pigs, dogs & cats
• Human moderately susceptible
• Hippopotamus, cape buffalo, elephants die due to anthrax
• Predators - carriers
• Elephant also affected.
PREVALENCE:
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• Disease is originated from sub Saharan Africa
• Prevalence - depends nature of soil & climatic condition
• Climate helps to determine the “forecast of anthrax year”.
• The infection remains in a particular area ® “Anthrax belts” or “Enzootic region”. Heavy rainfall following draught / dry summer following prolonged rain ->60F /15°C – spore is formed
• In Africa -Every summer with a heavy rain fall ®Devastating occurrence
• India - some region - Enzootic
ECONOMIC IMPACT:
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• Mortality
• Reduced milk yield
• Expenses incurred for vaccination
Zoonotic:
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• A fatal disease - human being
• Majorly an occupational hazard - inhalation of spores - while sorting out wool.
• Cutaneous anthrax : papules, vesicles in forearm, face & neck. These vesicles rupture & leaving necrotic ulcers in 1-2 days ® “Black eschar”.
• Pneumonic and GI tract infection – 100% mortality
PATHOGENESIS:
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Oozed out discharge from infected animals ® Anthrax bacilli exposed ® air ® spores produced ® spores ingested by the host ® vegetative form ® Spores proliferate ® regional draining LNs ® Vegetative form - Two virulent factors produced - poly D glutamic acid capsule & triple toxin- Organism traverse lymphatic vessels to reach Blood circulation ® septicemia ® invade ® all body tissues ® Lethal toxin ® Edema & tissue damage + blockage of capillaries ( “Log Jam” theory) ® death ¬ shock , acute renal failure & terminal anoxia.
At least 3x106 bacteria/ml necessary for causing death.
CLINICAL SIGNS:
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Cattle & sheep
Peracute form: No premonitory symptoms -Affected animals - dead
• Fever, muscle tremor, dyspnea &, congestion of mucous membrane
• Animal collapses & die after terminal convulsions
• Oozing unclotted blood ¬ nostrils, mouth, anus & vulva
Acute:
• Fever (42°C), severe depression, listlessness
• congestion & heamorrhage - deep mucosae
• increased heart rate & rapid respiration rate
• Mouth breathing - O2 hunger
• Local edema of tongue, throat, sternum, perineum & flanks -Pigs
• Abortion, decrease milk yield, blood stained or deep yellow color milk, diarrhea
Pigs:
Acutely & sub-acute infection
• High temperature, inflammation & edema of throat & face- distinct
• Painless swelling - obstruction - swallowing & respiration
• Blood stained froth – external orifices
• Peterchial hemorrahges - skin, dysentery
• No edema - throat
• Localization ® LNs of throat ® fatal septicaemia
Pulmonary form:
• Baby pigs - Lobar pneumonia & exudative pleurisy ® death - 1-2 days.
Horse:
• Acute, Septicaemic,
• Enteritis & colic
• Painful & edematous subcuataneous swellings - throat, over the lower neck, floor of the thorax & abdomen, prepuce & mammary gland - High fever, dyspnea
• Course of the disease - 48-96hrs
NECROPSY FINDING:
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• Absence of rigor mortis
• Quick assuming of the characteristic sawhorse posture
• Un-clotted tarry colored blood oozes out - natural orifices
• Soft, enlarged spleen -Black berry jam consistency
• carcass under suspect of anthrax should not be opened before confirm it by peripheral blood smear examination.
• Horses & pigs enlargement -Local LNs - Lesions - soft tissues of neck & pharynx -“Pharyngeal form of anthrax”.
DIAGNOSIS:
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Blood, edema fluid & smears - sealed leak proof container , in a sealed leak proof containers. Spleen & LNs for culture & histology
Poly Chrome Methylene Blue Staining : Square ended blue bacilli (chain) with metachromatic pink capsule - `McFadyeans reaction`.
In early stages- bacilli absent in blood. Culture done infected fluid or tissues - Injected - guinea pigs
Decomposed carcass does not have vegetative bacilli
Immunohistochemical - skin biopsies.
Gelatin stab culture: `inverted fir tree appearance`
Nutrient agar media: on 5% blood agar - `Medusa head colony`.
Ascolis test: Antigen & serum containing antibody react & produce – White precipitating ring
DIFFERENTIAL DIAGNOSIS:
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• Sudden death - farm animals suggestive of anthrax
• Lightening strike
• Peracute blackleg
• Malignant edema
• Bacillary hemoglobinuria
• Hypomagnesimia
• tetanus.
Treatment:
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• Recovery - identified & treated in early period
• Penicillin 20,000 IU /kg bw twice - 3 days
• Streptomycin 8-10g/day - Two divided doses i/m - cattle - effective
• Oxytetracycline 5mg /kg/day parentrally
• Antiserum 100-250ml - daily - 5 days - expensive.
CONTROL:
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• Disposal & destruction - burning / burial - carcass
• Burial - 2 meter deep - adequate application of quick lime, 5% formaldehyde -prevent the spread of spores
• disinfection - premises - 60°C heat (140F) & use of strong 5% Lysol - 2 days
• 5-10% solution - formalin / sodium hydroxide - highly effective
• Peracetic acid 3% solution - 8L/m2 - very good sporicide & effective sterilant
• Suspected animals quarantined -2wks.
• Vaccination - survivors,
• Administration – HIS - contact animals
• Trespass - milk & meat – not permitted
• Anthrax – materials should be handed to the laboratory - in person
VACCINE:
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Stern avirulent spore vaccine:
The solid strong immunity - last for almost 2 years - sheep & 1 year - cattle.
After vaccination - abortion, fever, decreased milk production occurs
No antibiotic should be used
Stern vaccine – neither shed in milk nor present in blood - 10 days - post vaccination
Milk should not be used 3 days post vaccination
Vaccinated animal - withheld from slaughter - 45days
Ring vaccination - endemic region - essential - contain outbreak
